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Results for “GRAVITATION”

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At least 1,639 records · Page 91Linked to original sources
PubMed1975

Gravitational effects on body composition in birds.

Gallinaceous birds, presenting a wide range of body size, were adapted physiologically to hyperdynamic environments, provided by chronic centrifugation. Chemical composition was measured directly on prepared carcasses, which were anatomically comparable, and more amenable to analysis than the intact body. Body mass and body fat decreased arithmetically with increasing field strength and also with increasing body mass. Water content of lean tissue increased in hyperdynamic environments, but irrespectively of body size.

Acceleration↗
PubMedDate not supplied

[Adaptation of the cardiovascular system to negative gravitation stresses during repeated antiorthostatic measures].

The cerebral, pulmonary, liver and peripheral circulation was studied simultaneously in 12 test subjects (aged 24--30) rheographically, photoplethysmographically and rheoplethysmographically; arterial pressure was measured by the Korotkoff method. The measurements were carried out during three antiorthostatic tests at --15degrees for 20 min or --30degrees for 20 min. It was shown that the cardiovascular system can adapt to repeated antiorthostatic exposures. The adaptation includes more significant decrease of the heart rate, increase in the systolic and pulse arterial pressure, fall of the diastolic arterial pressure, more marked reduction of antiorthostatically induced increase of blood filling and congestion of cerebral and pulmonary vessels, lesser decrease of their tone and blood redistribution into the vessels of the liver, upper and lower limbs. From the point of view of the adaptive effect repeated exposures to --15degrees are more effective.

Adaptation, Physiological↗
PubMed1997

Gravitation model for the magnitude of migration and its application.

"The magnitude of migration is one part of the feasibility study on migration, its result being critical to the yield of positive or negative effect.... The key to the success of migration is that the magnitude of migration must be limited within the capacity of the place of destination with generous room for flexibility. It is therefore necessary to determine the appropriate magnitude by scientific methods." The geographical focus is on China.

Asia↗
PubMed2003

[Effect of deafferentation on the size and myosin phenotype of muscle fibers during stretching of rat m. soleus and gravitational unloading].

The study was purposed to evaluate the contribution of the reflectory and local components during the chronic stretch of the postural muscle to the attenuation of the unloading-induced fiber size reduction and changes in the myosin heavy chain (MHC) profile. The surgical unilateral deafferentation (dorsal rhizotomy) was used. It was shown that unilateral deafferentation didn't influence on the amelioration of unloading-induced fiber size reduction in chronically stretched soleus muscle. Thus, the results obtained in the present study don't confirm the hypothesis, supposing the predominant contribution of the muscle afferent activation to the attenuation of unloading-induced fiber atrophy. Deafferentation of unloaded as well as control rats leads to the increase of the percentage of fibers expressing slow MYC isoforms.

Animals↗
PubMed2003

[Study of skeleton gravitation physiology and problem of osteoporosis].

Main osteoporosis definitions and some results of bone tissue research in Russian astronauts, patients, and healthy subjects, using modern osteodensitometry, are presented. Bone mineral density (BMD) was regularly decreased at lower segments of skeleton. In the skull bone and some other sites of upper part of skeleton, a tendency was revealed for an increase of the bone mineral content (BMC). The mean value of bone loss was within the normal range and not correlated with duration of space flight; it revealed a high individual variability and in some cases was clinically qualified as local osteopenia. On the ground of analysis of own results and animal and bone cultural experiments data in microgravity conditions, the described changes seem to be reflecting a deceleration of bone formation as an adaptive response of bone tissue to the mechanical unloading. The response is realized mainly on the tissue level. It does not exclude bone resorption activity as a result of changes in hierarchy of water and electrolytes metabolism as reflected by body fluid redistribution in cranial direction. The results obtained broaden our notions on pathogenesis of some types of osteoporosis in clinic.

Absorptiometry, Photon↗